Giant magnetocaloric effect in Co2FeAl Heusler alloy nanoparticles

TL;DR

This study reports a giant magnetocaloric effect in Co2FeAl Heusler alloy nanoparticles, with significant magnetic entropy change and cooling power near the Curie temperature, driven by a second-order phase transition.

Contribution

It demonstrates the magnetocaloric properties of Co2FeAl nanoparticles near Tc, highlighting their potential for magnetic refrigeration applications.

Findings

Magnetic entropy change of ~15 J/Kg-K at 1252 K under 14 kOe

Net relative cooling power of 89 J/Kg for 14 kOe field change

Second-order ferromagnetic to paramagnetic phase transition confirmed

Abstract

A giant magnetocaloric effect across the ferromagnetic (FM) to paramagnetic (PM) phase transition was observed in chemically synthesized Co2FeAl Heusler alloy nanoparticles with a mean diameter of 16 nm. In our previous report, we have observed a significant enhancement in its saturation magnetization (Ms) and Curie temperature (Tc) as compared with the bulk counterpart. Motivated from those results, here, we aim to explore its magnetocaloric properties near the Tc. The magnetic entropy change shows a positive anomaly at 1252 K. Magnetic entropy change increases linearly with the magnetic field, and a large value of ~15 J/Kg-K is detected under a moderate field of 14 kOe. It leads to a net relative cooling power of 89 J/Kg for the magnetic field change of 14 kOe. To confirm the nature of magnetic phase transition, a detailed study of its magnetization is performed. The Arrott plot and nature of the universal curve conclude that FM to PM phase transition in the present system is of second-order.